On August 20, 1974, scientists at Cornell University and the National Science Foundation used the radio telescope in Arecibo, Puerto Rico to beam a message into space. Encoded within the binary digits of the message was information related to the Solar System, our number system, basic chemistry, and human DNA.

1679 digits were used for the message on the presumption that "any sentient being" would recognize the number as the product of two prime numbers (23 and 73), allowing the digits to be then rearranged from a linear binary stream into a graphic format (depicted at left, enhanced with color for clarity).

The message has been traveling through space for 25 years and is not due to arrive at its destination for another 24,975 years. Curiously, however, a reply was received in 2001, in the form of a crop circle near the Chilbolton radio telescope, in Hampshire, UK. The "return message" inserts the element silicon into the vital chemical elements of life, and incorporates an extra strand in the DNA double helix. The size of the creature depicted in the reply is approximately 3'4", consistent with earthly reports of extraterrestrial visitations.

Makes me think of movies like Close Encounters and Independance Day, when they try to communicate via flashing sequences of lights. I'm from this planet and have no clue what that crap means, they may be missing the mark with this complicated lite-brite stuff.